1. Field of the Invention
The present invention relates to a display, and more particularly, a flat display.
2. Background of the Related Art
Keeping pace with current development of electronic technologies, new flat displays have been developed, which are thinner and lighter, and have a low power consumption according to recent trend of fabricating smaller sized, light weight, and low voltage products, such as a voltage driving type including LCD (Liquid Crystal Display), PDP (Plasma Display Panel), and VFD (Visual Fluorescent Display), and a current driving type including FED (Field Emission Display) and LED (Light Emitting Diode), and EL (Electroluminescence).
FIG. 1 illustrates a related art display device and the flat display driving circuit. A system interface 1 converts an external control signal or data into a control signal required for display device, and a memory 3 stores data of the control signal converted at the system interface 1. A data drive circuit 4 provides the data from the memory 3 to a plurality of data lines, and a control circuit 2 fixes identical duty ratios according to the control signal converted at the system interface 1. A scan drive circuit 5 provides a signal for the fixed duty ratio from the control circuit 2 to a plurality of scan lines. The plurality of scan lines and the plurality of data lines are formed to cross each other, and pixels at the cross points of the scan and data lines are made to selectively emit lights for displaying an image or character desired on display device.
FIG. 2 illustrates a drive timing diagram of a related art flat display and a displayed image according to the drive timing diagram. By selectively driving the scan lines and the data lines, resulting in turning on/off the dots/pixels at the cross points of the scan lines and the data lines, the image/text xe2x80x9cLGxe2x80x9d is displayed. During a first scan line is xe2x80x98onxe2x80x99, desired data lines are turned on for displaying a data at a desired position. In this type of display, a luminance of a displayed pixel is proportional to turn-on time periods of the scan line and the data line, and the turn-on time period of the scan line is varied with a size of duty ratio and one frame time period.
As shown in FIG. 3, if the duty ratio is set to be 1/40 and one frame time period is TF, each scan line turn-on time period is TF/ 40. When the flat display is driven such that all the turn-on time periods of the data lines are identical, all the pixels in a panel will exhibit the same luminance. When it is intended to display a line or a particular portion in the panel brighter than other portions, a high voltage or a high current is provided to a required data line. Alternatively, the turn-on time of the data line can be adjusted.
FIGS. 4A and 4B illustrate data driving circuits for a related art flat display wherein FIG. 4A illustrates a current driving type circuit and FIG. 4B illustrates a voltage driving type circuit. As shown therein, a data line in a display panel 7 desired to display brighter than other data lines are switched to a higher voltage or a higher current, for supplying the higher voltage or current thereto through a data driver 6.
The related art device and method for controlling a luminance of a flat display has various disadvantages. For example, a larger chip area is required for an additional circuit to provide the higher voltage or current to the data line. There is also some difficulty in always maintaining a stable voltage when the data driving circuit is the voltage driving type, or matching of respective current sources when the data driving circuit is the current driving type. Further, since the data line turn-on time control method requires a PWM (Pulse Width Modulation) circuit to all the data lines, a large chip area is required.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
An object of the present invention is to control a luminance of display device.
Another object of the present invention is to minimize a chip area.
A further object of the present invention is to reduce power consumption.
Still another object of the present invention is to change a duty ratio for adjusting a display time period of lines to control a luminance of a display device without additional power consumption.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device for controlling a luminance of a flat display includes a reference signal part for receiving an external video signal and providing a duty ratio of a scan signal and a video data desired to display, a controller for converting the duty ratio from the reference signal part and generating a remained scan time period, and a display part for receiving, and displaying the duty ratio converted at the controller and the video data.
The controller includes a frequency convertor for generating a plurality of clocks required for conversion of the duty ratio, a frequency selector for selecting one from the plurality of clocks as a reference clock, a duty ratio controller for setting up the selected reference clock as the duty ratio, a scan signal controller for generating a signal for driving the scan line in the set up duty ratio, and a display controller for synchronizing the duty ratio controller, and the scan signal controller.
The controller includes a scan controller for converting the duty ratio, to change a scan time period within which a scan can be driven for one frame period, and applying a remained scan time period to the scan line desired to display brighter than other scan lines additionally, and a data controller for driving a portion or entire data corresponding to the scan lines applied additionally, and masking the rest of the data.
In another aspect of the present invention, there is provided a method for controlling a luminance of a flat display, including the steps of (1) while frame frequencies are maintained the same, adjusting a duty ratio of a scan time period for generating a remained driving time period, (2) adding the generated remained driving time period to all scan lines desired to display brighter than other scan lines and driving the added scan lines, and (3) displaying only driving data on a plurality of data lines desired to display brighter while the driving data on rest of the data line are masked, for driving the data lines, selectively.
The present invention can be achieved in a whole or in parts by providing a driving circuit for a display device that includes a reference signal generator that receives video signal, the reference signal generator generating a first duty ratio and a video data, a controller receiving the first duty ratio and video data, the controller converting the first duty ratio to a second duty ratio when a luminance of a pixel of the display device is to be changed, the second duty ratio being less than the first duty ratio, a driver circuit that uses the second duty ratio and video data for displaying at least one of image and text.
The present invention can further be achieved in a whole or in parts by providing a controller for a display device that includes a scan controller circuit for converting a first duty ratio based on a first scan time period for each of a plurality of scan lines to a second duty ratio based on a second scan time period within which each scan line is driven for one frame period, and a data controller circuit for driving a portion or entire data corresponding to the scan lines.
The present invention can further be achieved in a whole or in parts by providing a display device that includes a input device receiving a video signal and generating a first duty ratio and video data, a controller that changes the first duty ratio to a second duty ratio, and a display panel having a plurality of scan lines and a plurality of data lines intersecting at a plurality of pixels, said plurality of scan lines being driven based on the second duty ratio and video data being provided to the plurality of data lines to display at least one of an image and text, wherein the second duty ratio is less than the first duty ratio when a brighter luminance is desired for a prescribed number of pixels.
The present invention can further be achieved in a whole or in parts by providing a method for controlling a luminance of a flat display, including the steps of (1) while a frame frequency is maintained, adjusting a duty ratio of a scan time period for generating additional scan time period, and (2) adding the additional scan time period to all scan lines desired to be displayed brighter than other scan lines.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.